GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 Yukon - 2WD 🢒 HVAC 🢒 Heating, Ventilation and Air Conditioning 🢒 Air Conditioning (A/C) Diagnostics - Pressure Zone A

Step

Action

Yes

No

1

Were you sent here from the A/C System Performance Test?

Go to Step 2

Go to Air Conditioning (A/C) System Performance Test

2

Refer to the air outlet temperatures recorded during the A/C system performance test.

Is there a 2 - 3 degrees difference or more in the discharge air temperature between the right and left center I/P outlets?

Go to Step 7

Go to Step 3

3

Did the customer concern mention that the A/C system output temperatures are good at first, but then turn warm during extended drives?

Go to Step 4

Go to Step 5

4

Increase engine speed to 2,000 RPM.

During extended operation of the A/C system, does the low side pressure decrease (possibly accompanied by heavy frost on the liquid line between the expansion device and the evaporator)?

Go to Air Conditioning (A/C) Diagnostics - Pressure Zone D

Go to Step 5

5

Refer to the pressures recorded during the A/C system performance test.

Inspect for the following conditions:

Caution: Refer to Moving Parts and Hot Surfaces Caution in the Preface section.

    • The high side pressure slightly above the specified pressure ranges but still within zone A on the A/C Pressure-Zone Classification Chart in the A/C System Performance Test. Refer to Air Conditioning (A/C) System Performance Test .
    • The discharge line is hot
    • The suction line is cool

Do the listed conditions exist?

Go to Step 7

Go to Step 6

6

Refer to the pressures recorded during the A/C system performance test.

Inspect for the following conditions:

Caution: Refer to Moving Parts and Hot Surfaces Caution in the Preface section.

    • The low side pressure slightly lower than the specified pressure ranges but still within zone A on the A/C Pressure-Zone Classification Chart in the A/C System Performance Test. Refer to Air Conditioning (A/C) System Performance Test .
    • The discharge line is warm-to-hot
    • The suction line is cool-to-warm

Do the listed conditions exist?

Go to Step 8

Go to Too Hot in Vehicle in HVAC Systems - Manual

OR

Too Hot in Vehicle in HVAC Systems - Automatic

7

The A/C system may be undercharged.

  1. Leak test A/C system. Refer to Leak Testing .
  2. Recharge the A/C system to specifications. Refer to Refrigerant Recovery and Recharging .

Is the repair complete?

Go to Step 14

--

8

The A/C system may be contaminated.

View the J 43600 information screen for detection of foreign gases in the A/C system.

Do foreign gases exist?

Go to Step 9

Go to Step 10

9
  1. Evacuate the A/C system to a scavenging tank. Refer to Refrigerant Recovery and Recharging .
  2. Recharge the A/C system to specifications.

Is the repair complete?

Go to Step 14

--

10

The A/C system may contain too much moisture or air.

  1. Evacuate and recharge the A/C system to specifications. Refer to Refrigerant Recovery and Recharging .
  2. Operate the A/C system and check the outlet air temperatures. Refer to Air Conditioning (A/C) System Performance Test .

Are the outlet temperatures within the specified ranges of the A/C Performance Test Table?

Go to Step 15

Go to Step 11

11

The A/C system may contain too much refrigerant oil.

  1. Recover the refrigerant from the A/C system. Refer to Refrigerant Recovery and Recharging .
  2. Remove the accumulator. Refer to Air Conditioning Accumulator Replacement .
  3. Drain and measure the refrigerant oil from the accumulator.

Was there more than 5 oz. of refrigerant oil drained from the accumulator?

Go to Step 12

Go to Step 13

12
  1. Reinstall the accumulator. Refer to Air Conditioning Accumulator Replacement .
  2. Flush the A/C system. Refer to the operating manual of the J 43600 for the flushing procedure.
  3. Add the specified amount of refrigerant oil to the A/C system. Refer to Refrigerant System Capacities .
  4. Recharge the A/C system. Refer to Refrigerant Recovery and Recharging .

Are the repairs complete?

Go to Step 14

--

13
  1. Add the specified amount of refrigerant oil to the A/C system. Refer to Refrigerant System Capacities .
  2. Install the accumulator. Refer to Air Conditioning Accumulator Replacement .
  3. Recharge the A/C system. Refer to Refrigerant Recovery and Recharging .

Are the repairs complete?

Go to Step 14

--

14
  1. Record the low and high side pressures and the IP outlet air temperature.
  2. Compare the outlet temperatures to those listed in the A/C System Performance Chart. Refer to Air Conditioning (A/C) System Performance Test .

Are the high and low side pressures and outlet temperatures within specifications?

Go to Step 15

Go to Air Conditioning (A/C) System Performance Test

15

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Symptoms - HVAC Systems - Manual in HVAC Systems Manual

OR Symptoms - HVAC Systems - Automatic in HVAC Systems Automatic